After a number of children died when their parents left them locked inside hot cars, a number of companies developed aftermarket sensors to detect whether children had been left in a vehicle. Unfortunately, the National Highway Traffic Safety Administration (NHTSA) recently revealed many of these devices are not reliable.

"While we feel these devices are very well-intended, we don't think they can be used as the only countermeasure to make sure that you don't forget your child behind in a car," NHTSA administrator David Strickland told Bloomberg News.

According to Strickland, the devices on the market today generally work, but are not free from defects. The NHTSA pointed to a recent study that showed short circuits, interference from electronic systems, accidental disarming and other issues cropping up with these aftermarket products. Because of this, the NHTSA urges all parents to take other steps beyond simply relying on these devices as reminders.

Currently, no automaker offers a factory-installed safety system for detecting whether a child is left in a vehicle - possibly because automakers are held to the NHTSA's strict standards when designing safety devices.

Drivers need to also keep child safety in mind when the vehicle is in motion as well. Properly inflating tires and getting regular brake service can help avoid accidents on the road.